Machinist&#39;s protractor.



No. 744,963. PATENTED NOV. 2&1, 1903. C. T. FRANTZ.

- MAGHINISTS PROTRAGTOR.

APPLIOATION FILED FEB. 17. 1902.

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Patented November 24:, 1908.

Ilnrrn STATES ATFNT Christ.

CHARLES T. FRANTZ, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO CHARLES H. JOY, OF CHICAGO, ILLINOIS.

MACHINlSTS PROTRACTOR.

SPECIFICATION forming part of Letters Pateiat No. 744,963, dated November 24:, 1903.

Application filed February 1'7, 1902. $erial No. 94,436. (No model.) i

' act specification.

The object of my invention is to provide a simple and convenient form of protractors which will enable a machinist to accurately and easily obtain any angle desired up to one hundred and eighty (180) degrees and to conveniently manipulate the same flat upon the work. This I accomplish by the means hereinafter fully described and as particularly pointed out in the claims.

In the drawings, Figure 1 is a plan View of my invention, showing a portion of the legs thereof broken away. Fig. 2 is a side edge view of the same. Fig. 3 is a plan view of the under side of the central portion of the protractor,having the portions thereof radiating therefrom broken away. Fig. 4 is a crosssection taken on dotted line 4 i, Fig. 3. Fig. 5 is a plan view of a fragment of the segmental portion of the quadrant, showing the under surface.

In the drawings, A represents a flat steel quadrant, which has its central portion, or, in other words, all except its marginal portions, cut away to obtain the desired lightness. The segmental edge a of this quadrant is preferably undercut, and its upper surface of the segmental portion particularly, and, if desired, its under surface, is provided with a series of graduations b, numbering from one (1) degree to ninety (90) degrees on its upper surface (reading from right to left) and from ninety (90) to one hundred and eighty (180) degrees on its under surface. The radial planes striking through degrees one (1) and ninety (90) are parallel to and come midway between the edges of the radial members 00 and y of the quadrant A, and at the vertex of these planes a blade 13 is pivoted thereto by a suitable pivot-nut C. Blade B is preferably of the same width as the radial members at and y of the quadrant and is of such length that the branch r thereof, which is ad justably movable over the quadrant, extends just beyond the segmental edge a thereof and has its end edge e bent downward and inward, so as to grip and be retained by the undercut edge a of said quadrant. About midway between the longitudinal edges of the segmental portion of quadrant A is a segmentally-arranged series of holes d (Z, with the center of each of which some one of the radial graduations b aline. These holes are engaged by the end of a thumb-nut D, tapped through the center of width of blade B, and in order that the operator may make no mistake and correctly adjust the blade in radial alinement with any particulargraduation I prefer to provide the end of said blade B between said thumb-nut D and the downturned edge e thereof with an openingf and with an indicator-point g projecting longitudinally from one side of it, so as to facilitate such correct adjustment of blade B to any degree desired. The end of the straight side portion 3 of the quadrant near which blade B is pivoted and which parallels the radial plane striking through degree 0 of the quadrant is rounded on a curve struck from the pivotal center of said blade B, thus causing an angular recess 71, one side of which will be bound by the end and of the straight side portion 1 of the quadrant and the curved .end edge of the other straight side portion 51:.

Projecting. at right angles to portion'y of the quadrant and so that its straight edge E will aline with the transverse plane of the end edge of said portion 00 is a leg F. This leg corresponds in length to that of the adjacent cooperating branch 8 of the blade 13, which latter is made just twice as thick between the curved or rounded end of portion y and its end, so that when adjusted to aline with the radial plane striking through degree 0 of the quadrant the adjacent straight'edges of leg F and branch 8 will come fiat together and when said blade is adjusted so as to aline with any ,other degree will form the sides of a perfectangle of less than ninety (90) degrees corresponding thereto. \Vhenever it is desired to get the sides of an angle of a degree greater than ninety (90) degrees, the blade is adjusted to aline with the radial plane of such greater degree, (the graduations of which appear on the under side of the segmental ICO portion of the quadrant,) whereupon the outer straight edge of portion or of the quadrant and the outer straight edge of branch 5 of blade B will describe the sides of the desired obtuse angle.

As manufacturing the quadrant and leg F out of one solid piece of sheet metal would involve a great waste of material, I prefer to make said leg of a separate strip of metal and to decrease the width of the end 7c thereof lapping over and secured to the part of the quadrant adjacent to the pivot of blade B one-half and to seat such reduced end 7c ina groove K in the quadrant, as shown, and rivet it by rivets m to the same. The heads of the rivets m, as well as the head of pivot-bolt C, (which latter is next the under side of quadrant A,) are ground so as be flush with the plane of the fiat sides of said quadrant.

It will be noticed that my invention can lay flat upon the work, or when the plotting is near the straight edge of work the apparatus can be reversed and blade B brought to bear against such straight edge to obtain the proper angle.

What I claim as new is 1. A protractor consisting of a graduated quadrant the segmental edge of which is undercut and which has a leg extending at right angles to one of the radial sides thereof next the center, and having a blade pivoted at the center of said quadrant one branch of which is adjustable on said quadrant and has its end extended beyond the segmental edge thereof and bent downward to engage the same, and the other branch of which cooperates with the leg of said quadrant.

2. A protractor consisting of a graduated quadrant the segmental edge of which is undercut and which has a leg extending at right angles to one of the radial sides thereof next the center, and having a blade pivoted at the. center of said quadrant one branch of which is adjustable on said quadrant and has its end extended beyond the segmental edge thereof and bent downward to engage the same, and the other branch of which cooperates with the leg of said quadrant, and is thicker than said adjustable branch.

3. A protractor consisting of a quadrant the segmental edge portion of which is graduated to indicate circu mferent-ial degrees and is provided with a segmental series of holes intersected by said grad nations, and a leg Inadeintegral with said quadrant projecting at right angles to one of the radial sides of said quadrant next the center thereof, in combination with a blade pivoted at the center of said quadrant one branch of which is adjustable on the same and the other cooperating with the leg thereof, the last-named part being of greater thickness than the first-named part, and a thumb-nut tapped through the adjustable branch of said blade and engaging said holes.

4. A protractor consisting of a quadranthaving the undercut segmental edge portion thereof graduated and provided with a segmentally-arranged series of holes therein which are intersected bysaid graduations,and

a leg integral with and projecting at right an- 1 gles to one of the radial sides of said quadrant next the center thereof, in combination with a blade pivoted at the center of said quad rant one branch of which is adjustable on the same and has its end edge bent so as to engage the und ercut segmental edge of the quad ran t, and the other branch of which cooperates with said leg, and a thumb-screw or nut tapped through the adjustable branch of said leg and en gaging said holes. 7

CHARLES T. FRANTZ. 

